26/30 kW Interface Panel 1 Inverter CEI 0-21
Icierre QAC 26/30 kW (1 INV) three-phase interface panel for 26 to 30 kW photovoltaic systems with a single inverter: 50 A at 400 V, compliant with the Italian grid code CEI 0-21.
Main switch with backup shunt trip, residual current circuit breaker dedicated to the inverter line, 50 A AC-3 interface contactor, SPI relay and class II SPD in a 72-module IP66 class II fibreglass enclosure. Supplied with single-line diagram, declaration of conformity and SPI test report.
The Icierre QAC 26/30 kW (1 INV) is the three-phase interface panel designed for a 26 to 30 kW photovoltaic system connected through one single inverter. It is delivered wired and factory-tested, rated 50 A at 400 V and compliant with CEI 0-21, the Italian standard for connecting generators to the low-voltage grid. On board are all the functions the grid operator requires at this size: main device, interface device, interface protection and backup trip.
Two protection levels: main switch and inverter line
What sets this configuration apart is its two-level architecture. At the top sits the Main Device (DG), a 4x50 A 6 kA circuit breaker fitted with a shunt trip coil with backup function: if the interface contactor fails to open when the SPI relay commands it, the main device disconnects the system from the grid. Downstream, the line feeding the inverter has its own 4x50 A 6 kA 300 mA type A residual current circuit breaker.
In practice, a fault on the cable or on the inverter trips the protection of that line without involving the main switch, and during maintenance the inverter is isolated by a dedicated device. This is the difference from the 2 INV version of the same size, which splits the power over two separately protected lines for two inverters: here there is a single line using the full 50 A rating.
QAC 26/30 kW (1 INV) technical specifications
| System power | 26 to 30 kW, 1 three-phase inverter |
| Rated current | 50 A |
| Voltage | 400 V three-phase |
| Main device (DG) | Circuit breaker 4x50 A, 6 kA, with shunt trip coil and backup function (DDR) |
| Inverter line protection | Residual current circuit breaker 4x50 A, 6 kA, 300 mA type A |
| Interface device (DDI) | 4P contactor 50 A in AC-3, 230 V coil, auxiliary contacts 2NO/2NC |
| Interface protection (SPI) | Relay compliant with CEI 0-21 |
| Surge protection (SPD) | Three-phase 4P class II, Imax 20 kA, 440 Vac |
| Auxiliary circuits | 2 fuse holders 1P+N with 6 A fuses (SPI supply and UPS/auxiliaries), 1 fuse holder 3P+N with 2 A fuses (SPI measurements) |
| Provisions | DDI/M2 in/out, external trip, IN/OUT for external UPS |
| Terminal blocks | Cable entry and exit from the bottom, 25/35 mm² |
| Enclosure | 72-module thermosetting fibreglass box, IP66, class II |
| Dimensions | 450 x 660 x 220 mm |
| Reference standard | CEI 0-21 |
When it is needed and how to size it
CEI 0-21 requires an interface protection system external to the inverter for low-voltage systems above 11.08 kW: at 26-30 kW the panel is therefore mandatory. Sizing takes one calculation: 30 kW three-phase at 400 V corresponds to about 43 A at unity power factor, 26 kW to about 38 A. The 50 A rating covers the whole range with margin, while below 25 kW the smaller size is the better choice, with protections coordinated to the real current.
At this power level many markets also add administrative, fiscal or metering obligations for the generator: it is worth checking them with the local grid operator and authorities at the design stage.
What is included
- Wired and tested panel, ready for mounting and connection
- Single-line diagram of the panel
- Declaration of conformity
- SPI test report, the record verifying the interface relay settings
Not included: the external UPS, for which the panel is only prepared, and the DC-side protections, which are provided by the string combiner box.
Frequently asked questions
What is the difference between the QAC 26/30 kW 1 INV and 2 INV?
The 1 INV version has a single output line protected by a 4x50 A residual current circuit breaker and is designed for one 26-30 kW inverter. The 2 INV version splits the power over two lines with separate protections, for systems using two smaller inverters. The rest of the panel, namely the main switch with backup trip, the DDI contactor, the SPI relay and the SPD, is the same.
Can I use it with a 20 or 25 kW inverter?
It would work, but it is not the right choice: at 20-25 kW the operating current is 29-36 A and 50 A protections would be oversized for the cables and the inverter. For those power levels there are the QAC 16/20 kW and 21/25 kW sizes, with breakers coordinated to the real current.
What is the UPS provision for?
The panel has dedicated terminals for connecting an external uninterruptible power supply to the auxiliary circuit of the SPI relay. This keeps the interface protection powered during grid disturbances or outages, when the design or the grid operator requires it. The UPS is not included.
Is the type A residual current device compatible with my inverter?
Many transformerless three-phase inverters have internal residual current monitoring and accept a type A device upstream, like the one fitted here. Some manufacturers, however, require type B: check the installation manual of the chosen inverter before ordering.
Which panel documents are needed for the grid connection application?
The grid operator asks for the single-line diagram, the declaration of conformity and the SPI relay test report: for the panel, all three are included in the supply. The installer remains responsible for the declaration of conformity of the complete system and the site-specific data.